Magnetic self-assembly for integrated circuit packages

ABSTRACT

An integrated circuit package may include a substrate and an integrated circuit. The substrate may include at least one region, and a first magnetic material associated with the at least one region. The integrated circuit may have a second magnetic material associated therewith. The second magnetic material may be attracted to the first magnetic material to coupled the integrated circuit to the at least one region of the substrate. The IC package may be utilized in an RFID tag of an RFID system. An associated method for assembling an integrated circuit to a substrate is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/074,114, filed Mar. 7, 2005 entitled MAGNETIC SELF-ASSEMBLY FORINTEGRATED CIRCUIT PACKAGES, now U.S. Pat. No. 7,615,836, the entiredisclosure of which is hereby expressly incorporated by reference.

FIELD OF THE INVENTION

This disclosure relates to integrated circuits, and in particular, tointegrated circuit packages formed using magnetic self-assembly. Theintegrated circuit packages may be utilized in a variety of systems suchas in a radio frequency identification (RFID) system.

BACKGROUND OF THE INVENTION

Integrated circuits (ICs) are utilized in a variety of electronicdevices to perform a myriad of functions. Integrated circuits may bepackaged with a substrate to protect the IC and to provide electricalconnections from the substrate to the contacts of the IC. In general,functionality provided by ICs has increased over the years while ICcosts have decreased. However, the costs associated with packaging an ICwith a substrate have not experienced a comparative cost reduction. Infact, packaging costs may even increase in the future given the trendtowards reduced IC sizes and complicated interconnection schemes.

One conventional method of connecting an IC to a substrate involvesplacing the IC on the substrate, either manually or using a robotic arm.This conventional process requires human intervention and/or complexrobotic machinery and becomes increasingly difficult as IC sizesdecrease. This conventional process also usually requires a wire-bondingprocess to electrically connect contact pads of the IC to othercomponents or terminals.

Another conventional method of connecting an IC to a substrate involvesuse of fluid flow. The fluid flow method involves creation of aplurality of shaped recesses in a substrate configured to mate withcorrespondingly shaped ICs. A slurry containing a plurality of theshaped ICs is directed over the substrate, and the ICs fall into therecesses in the substrate. The substrate may be examined for emptyrecesses and other devices such as a robotic arm may then place ICs intothe empty regions. This fluid flow approach requires formation ofparticularly shaped recesses in the substrate, which requires additionalprecision and cost. The ICs must also be precisely manufactured withcomplimentary mating geometries to mate with the recesses. Furthermore,the fluid flow approach can leave an excessive number of empty recesseson the substrate, since gravity may be the only force urging the ICsinto the recesses.

Accordingly, there is a need for a magnetic self-assembly for integratedcircuit packages to simplify IC package manufacturing and reducemanufacturing costs. Such a method may be used in a variety ofapplications and systems. One application may be to manufacture RFIDtags at reduced costs compared to conventional methods. Such RFID tagsmay be used in an RFID system for tagging retail merchandise where thecost of the RFID tag is an important factor.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the claimed subject matterwill become apparent as the following Detailed Description proceeds, andupon reference to the Drawings, where like numerals depict like parts,and in which:

FIG. 1 is block diagram of a RFID system for use in a retailenvironment;

FIG. 2A is an exploded cross-sectional view of an IC and substrate foraccepting the IC;

FIG. 2B is a cross-sectional view of the IC and substrate of FIG. 2Awhere the IC is coupled to the substrate;

FIG. 3 is a cross-sectional view of an electrical connection formedbetween an IC and substrate;

FIG. 4 illustrates an embodiment of a magnetic keying arrangement toparticularly position the IC on the substrate;

FIGS. 5 and 6 illustrate magnetization arrangements of magneticmaterial; and

FIG. 7 illustrates operations according to an embodiment.

Although the following Detailed Description will proceed with referencebeing made to illustrative embodiments, many alternatives,modifications, and variations thereof will be apparent to those skilledin the art. Accordingly, it is intended that the claimed subject matterbe viewed broadly.

DETAILED DESCRIPTION

Systems and methods consistent with the present invention will bedescribed herein in connection with various embodiments. Those skilledin the art will recognize that the features and advantages of thepresent invention may be implemented in a variety of configurations. Itis to be understood, therefore, that the embodiments described hereinare presented by way of illustration, not of limitation.

FIG. 1 illustrates an RFID system 100 utilized in a retail environment102. The RFID system 100 may include a plurality of RFID tags 106-1,106-2 . . . 106-n and an RFID reader 112. Each of the RFID tags 106-1,106-2 . . . 106-n may be affixed to an associated article 104-1, 104-2 .. . 104-n presented for purchase in the retail environment 102. The RFIDreader 112 may be portable or may be fixed to a particular location,e.g., to a location proximate a point-of-sale (POS) station 108. TheRFID reader 112 may scan for RFID tags 106-1, 106-2 . . . 106-n bytransmitting an interrogation signal at a known frequency. RFID tags mayrespond to the interrogation signal with a response signal containing,for example, data associated with the article to which it is affixed.The RFID reader 112 may include processing capabilities to detect theresponse signal and decode the data. Since the RFID system 100 utilizesradio wave signals to communicate data, no line of sight between theRFID reader 112 and RFID tags 106-1, 106-2 . . . 106-n is required.

One or more of the RFID tags, as shown in connection with RFID tag106-n, may include an IC package 115 including an IC 120 coupled to asubstrate 122. As used herein, an “integrated circuit” or IC means asemiconductor device and/or microelectronic device, such as, forexample, a semiconductor integrated circuit chip. The substrate 122 mayinclude an antenna. The IC 120 may include computer processingcapabilities and a certain amount of memory depending on the type ofRFID tag 106-n. The IC package 115 of the RFID tag 106-n may bemanufactured according to the embodiments detailed herein to enableassociated cost reductions in the manufacture of RFID tags. Of course,IC packages manufactured according to the magnetic self-assemblyembodiments detailed herein may also be utilized in a variety of othersystems and devices.

FIG. 2A is an exploded view of an integrated circuit package 200including a substrate 202 and an IC 204. The substrate 202 may be formedfrom a variety of materials including flexible materials and may includeone or more regions 212 to mate with the IC 204. In some embodiments,the region 212 may be recessed relative to a top surface of thesubstrate. A recessed region may be provided in any geometric shape andmay be dimensioned to accept at least a portion of the IC 204. In oneembodiment, the recessed region may be configured to mate with acorrespondingly shaped IC.

The substrate 202 may include a first magnetic material 216 associatedtherewith. The first magnetic material may, for example, be disposed onor beneath a surface of the region 212. A second magnetic material 218may be associated with the IC 204. For example, the second magneticmaterial may be disposed on or beneath a surface of the IC. Although thefirst 216 and second 218 magnetic materials are illustrated as havingparticular orientations relative to the substrate and IC, respectively,it is to be understood that the magnetic materials may be associatedwith the IC and substrate by providing the material completely orpartially on a surface, completely or partially beneath a surface, orintegral with the IC or substrate. Also, the magnetic materials may beprovided at any location on or within the IC or substrate.

The first and second magnetic materials 216, 218 may, for example,include high energy metallic magnetic materials. Examples of suchmaterials include, but are not limited to iron platinum, cobaltplatinum, and copper. As the IC 204 is transported about the substrate202 by any of a variety of techniques, it is, aided into position, e.g.as shown in FIG. 2B, by the magnetic attraction between materials 216and 218.

FIG. 3 illustrates another embodiment of an IC package 300 that providesfor magnetic self-assembly of the IC 204 a to the substrate 202 a andalso facilitates formation of an electrical connection between the IC204 a and the substrate 202 a. In the embodiment of FIG. 3, the region212 of FIG. 2A may be a recessed region 212 a. The IC 204 a may includea contact pad 302. Although only one contact pad 302 is illustrated forclarity, the IC 204 a may include a plurality of contact pads. Thesecond magnetic material 218 a may be disposed on the contact pad 302.In addition, a conductive material 304 may initially be attached to thesecond magnetic material 218 a. Alternatively, the conductive materialmay initially be attached to the first magnetic material 216 a.

The conductive material 304 may be a conductive adhesive in oneembodiment such as a thermally activated conductive adhesive. In oneexample, the conductive adhesive may be a conductor-filled thermal setadhesive film such as the Z-Axis Adhesive Film 7303 by 3M Corporation.In other examples, the conductive adhesive 304 may be a thermoplasticconductive adhesive or a non-heat activated conductive adhesive such asa room temperature adhesive. The conductive material 304 may also besolder. The solder may be applied as a solder paste or applied to formsolder bumps. The first magnetic material 216 a may be positioned in oron the recessed region 212 a with an exposed portion that contacts theconductive material 304, as shown, for example, in FIG. 3.

As the IC 204 a is attracted into the region of the substrate 202 a bythe magnetic attraction of the first and second magnetic materials 216a, 218 a, the first and second magnetic materials 216 a, 218 a maybecome affixed to each other via the conductive material 304 to form anelectrical connection between the IC 204 a and circuitry 308 of thesubstrate 202 a. As used herein, “circuitry” may include, for example,singly or in any combination, hardwired circuitry, programmablecircuitry, state machine circuitry, and/or firmware that storesinstructions executed by programmable circuitry. In one RFID tagembodiment, the circuitry 308 may comprise an antenna 309 and the firstmagnetic material 216 a may be deposited at an input port to theantenna.

To make the electrical connection between the IC 204 a and the substrate202 a permanent when using a thermally activated conductive material,heat may be applied to the material and pressure may be applied to urgethe first and second magnetic material 216 a, 218 a towards each other.The heat may be sufficient to bond the first and second materials 216 a,218 a to the conductive material 304 to form a permanent electricalconnection between the IC 204 a and the substrate 202 a.

In some embodiments, a particular orientation of the integrated circuitrelative to the substrate may not be critical. This may be the case forsome RFID tag embodiments. In this instance, one of the first or secondmagnetic materials 216 or 218 associated with the substrate 202 or theIC 204 may be a soft magnetic material, such as a nickel or iron-basedalloy. The other of the first and second magnetic materials may have apermanent magnetization such as from a permanent magnet. In thisembodiment, as the soft magnetic material moves closer to the field ofthe permanent magnet, the soft magnetic layer may be attracted to thepermanent magnet.

In other embodiments, a particular orientation of the IC relative to thesubstrate may be desired. FIG. 4 illustrates an embodiment of a magnetickeying arrangement to particularly position the IC 404 relative to thesubstrate 402. The IC 404 is illustrated with its mating side facingoutward, and has a rectangular configuration. A plurality of contactpads 440, e.g. sixteen in the illustrated embodiment, may be provided onthe IC and the second magnetic material 418 may be disposed on each ofthe plurality of contact pads to establish an arrangement of North (N)and South (S) magnetization polarities keyed to an associatedarrangement in a substrate.

The substrate is shown in top view and includes a top surface 403 with arectangular region 412 formed thereon. In the illustrated exemplaryembodiment, the region 412 is adapted to mate with and receive the IC404. The first magnetic material 416 may be disposed on or within abottom surface of the region and may be magnetized to establish amagnetization polarity arrangement keyed to arrangement on the IC.

As shown, for example, side 420 of the first magnetic material 416 mayhave polarities N, S, S, N to attract the side 430 of the IC 404 havingpolarities S, N, N, S, respectively. Side 422 may have polarities S, N,S, N to attract polarities N, S, N, S, respectively, of side 432 of theIC 404. Side 426 may have polarities N, S, N, S to attract polarities S,N, S, N, respectively, of side 436 of the IC. Finally, side 424 may havepolarities N, N, S, S to attract polarities S, S, N, N, respectively, ofside 434 of the IC. The arrangement of magnetic polarities on thesubstrate and the IC thus establishes a magnetic keying arrangementwhereby the IC 402 may be attracted to a particular orientation on thesubstrate.

The second magnetic material 218 on the IC 204 may have a variety ofmagnetization arrangements. FIG. 5 illustrates one embodiment of thesecond magnetic material 218 b having a perpendicular magnetizationarrangement that may be disposed on a contact pad 500 of an IC. FIG. 6illustrates another embodiment of the second magnetic-material 218 chaving a longitudinal magnetization arrangement that may be disposed ona contact pad 600.

To provide a more compact IC package assembly, an array of lead-frameelements may be used to assemble the ICs. The lead-frame elements may beused to make connection to an antenna substrate through ultrasonicsealing or other methods. The lead-frame elements may be a dense arrayto facilitate a more compact IC package assembly.

FIG. 7 is a flow chart of operations 700 consistent with an embodimentfor assembling an IC to a substrate. Operation 702 may include providinga first magnetic material associated with at least one region of thesubstrate. Operation 704 may include providing an integrated circuithaving a second magnetic material associated therewith. Finally,operation 706 may include transporting the integrated circuit about thesubstrate, whereby the second magnetic material is attracted to thefirst magnetic material to urge at least a portion of the integratedcircuit towards the at least one region. One of several ways totransport the integrated circuit about the substrate may includeproviding a slurry including one or more ICs and a fluid and directingthe fluid over the substrate.

According to one aspect of the invention, there is provided anintegrated circuit package including a substrate and an integratedcircuit. The substrate may include at least one region, and a firstmagnetic material may be associated with the at least one region. Theintegrated circuit may have a second magnetic material associatedtherewith. The second magnetic material may be attracted to the firstmagnetic material to couple the integrated circuit to the at least oneregion of the substrate.

According to another aspect of the invention, there is provided an RFIDtag. The RFID tag may include a substrate and an integrated circuit. Thesubstrate may include at least one region, and a first magnetic materialassociated with the at least one region. The substrate may furtherinclude an antenna for transmitting signals to and receiving signalsfrom an associated RFID reader. The integrated circuit may have a secondmagnetic material associated therewith. The second magnetic material maybe attracted to the first magnetic material to couple the integratedcircuit to the at least one region of the substrate.

According to another aspect of the invention, there is provided a methodof assembling an integrated circuit to a substrate including providing afirst magnetic material associated with at least one region of thesubstrate; providing an integrated circuit having a second magneticmaterial associated therewith; and transporting the integrated circuitabout the substrate, whereby the second magnetic material is attractedto the first magnetic material to urge at least a portion of theintegrated circuit towards the at least one region.

Advantageously, in these embodiments the magnetic attraction of thefirst and second magnetic materials allows for magnetic self-assembly ofan IC to a region of a substrate. This provides for efficientself-assembly reducing the need for higher priced conventionalalternatives such as “pick and place” machines. This results in reducedIC packaging costs. In addition, the first and second magnetic materialsmay be utilized, e.g., together with a conductive material, to also forman electrical connection between the IC and circuitry of the substrate.As such, conventional wire-bonding processes and its associatedcomponents and costs may be avoided. The attraction of the first andsecond magnetic materials may also provide for better IC alignment thanconventional alternatives such as a pick and place machine. The ICpackage manufactured according to magnetic self-assembly embodimentsdescribed herein may be utilized in a variety of devices and systems.One example is to manufacture RFID tags at reduced costs compared toconventional methods. Such RFID tags may be used in an RFID system fortagging retail merchandise in a retail environment where the cost of theRFID tag is an important factor.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention,in the use of such terms and expressions, of excluding any equivalentsof the features shown and described (or portions thereof), and it isrecognized that various modifications are possible within the scope ofthe claims. Other modifications, variations, and alternatives are alsopossible. Accordingly, the claims are intended to cover all suchequivalents.

1. A method of assembling an integrated circuit to a substratecomprising: providing a first magnetic material associated with at leastone region of said substrate; providing an integrated circuit having asecond magnetic material associated therewith; directing a slurrycomprising said integrated circuit and a fluid over said substrate; andtransporting said integrated circuit towards said at least one region ofsaid substrate, whereby said second magnetic material is attracted tosaid first magnetic material to urge at least a portion of saidintegrated circuit towards said at least one region.
 2. The method ofclaim 1, wherein one of said first and second magnetic materialscomprises a permanent magnet and the other of said first and secondmagnetic materials comprises a magnetic material attracted to saidpermanent magnet.
 3. A method of assembling an integrated circuitpackage, comprising: providing a substrate having circuitry therein:providing a first magnetic material associated with at least one regionof said substrate; providing an integrated circuit having a secondmagnetic material associated therewith wherein said integrated circuitcomprises at least one contact pad and said second magnetic material isdisposed on said at least one contact pad; transporting said integratedcircuit over said substrate toward said at least one region, wherebysaid second magnetic material is attracted to said first magneticmaterial to urge at least a portion of said integrated circuit towardssaid at least one region; establishing an electrical connection betweensaid integrated circuit and said circuitry of said substrate throughsaid first magnetic material and said second magnetic material; andelectrically and magnetically coupling said integrated circuit to saidat least one region of said substrate.
 4. The method of claim 3, furthercomprising: applying a conductive material to one of said first andsecond magnetic materials; and positioning said first and secondmagnetic materials so that said conductive material contacts said firstand second magnetic materials when said integrated circuit is depositedin said at least one region to establish an electrical connectionbetween said integrated circuit and circuitry of said substrate.
 5. Themethod of claim 4, wherein said conductive material comprises athermally activated conductive adhesive and said method furthercomprises: heating said thermally activated conductive adhesive; andapplying pressure to first and second magnetic materials to form saidelectrical connection.
 6. The method of claim 3 wherein said circuitrycomprises an antenna of an RFID tag.
 7. The method of claim 3 whereinsaid first magnetic material comprises a plurality of polarities andsaid second magnetic material comprises a plurality of polarities toprovide a desired orientation of said integrated circuit in said atleast one region.
 8. The method of claim 3, wherein one of said firstand second magnetic materials comprises a permanent magnet and the otherof said first and second magnetic materials comprises a magneticmaterial attracted to said permanent magnet.
 9. The method of claim 3,wherein said step of transporting said integrated circuit over saidsubstrate toward said at least one region comprises directing a slurrycomprising said integrated circuit and a fluid over said substrate. 10.The method of claim 3, wherein said step of transporting said integratedcircuit over said substrate toward said at least one region comprisesvibrating said substrate.
 11. The method of claim 1, wherein said firstmagnetic material comprises a plurality of polarities and said secondmagnetic material comprises a plurality of polarities to provide adesired orientation of said integrated circuit in said at least oneregion.
 12. The method of 1, wherein the substrate contains circuitry,and said circuitry comprises an RFID antenna.
 13. A method of assemblingan integrated circuit to a substrate comprising: providing a firstmagnetic material associated with at least one region of said substrate;providing an integrated circuit having a second magnetic materialassociated therewith; vibrating said substrate to transport saidintegrated circuit over said substrate towards said at least one region,whereby said second magnetic material is attracted to said firstmagnetic material to urge at least a portion of said integrated circuittowards said at least one region.
 14. The method of claim 13, whereinone of said first and second magnetic materials comprises a permanentmagnet and the other of said first and second magnetic materialscomprises a magnetic material attracted to said permanent magnet. 15.The method of claim 13, wherein said first magnetic material comprises aplurality of polarities and said second magnetic material comprises aplurality of polarities to provide a desired orientation of saidintegrated circuit n said at least one region.
 16. The method of 13,wherein the substrate contains circuitry, and said circuitry comprisesan RFID antenna.